There are known connecting devices requiring the transverse drilling of the ends of the tubular elements in order to connect said tubular elements for assembling structures for use as shelves, tables, exhibitors, and the like. Consequently the lengths of the elements must be predefined during the manufacturing phase, since they cannot be easily changed.
There are known connecting devices allowing the connection between tubular elements without fixing holes, but said connecting devices are external with respect to said tubular elements.
The main drawback of said known devices consists in that they are bulky and very visible, so affecting the aesthetics of the whole structure. A further drawback of said known devices consists in that it is necessary to loosen several connecting devices, in order to modify the position of an element.
Document DE 94 13 840 U discloses a connecting device suitable for tubular elements fit for constructing modular structures, wherein said connecting device includes insert means having an expandable portion and a head, shells each provided with a plurality of housing having a shape approximately complementary to the head; fixing, means to fix the head to a related housing.